Well, I finally managed to correctly overclock my AMD Athlon64 3000+ from 1.8GHz to 2.25GHz safely (well, as safe as can be)

The default setting that I had to change

FSB Speed: 200MHz
HT Multiplier: x5
CPU Multiplier: x9
CPU VCore: 1.450v + 0%
RAM Clock: 200MHz

This results in

CPU Speed: 1800MHz [FSB x CPU Multiplier] = [200 x 9]
DDR Clock: 200MHz [Ratio of FSB Speed to RAM Clock (1:1 in this case)]
Bus Speed: 1000MHz [FSB Speed x HT Multiplier] = [200 x 5]

In order to overclock to 2.25GHz I had to change these settings to

FSB Speed: 250 MHz
HT Multiplier: x4
CPU Multiplier: x9
CPU VCore: 1.450v + 6.6% (1.545v)
RAM Clock: 166MHz

This results in

CPU Speed: 2250MHz [FSB x CPU Multiplier] = [250 x 9]
DDR Clock: 208MHz [Ratio of FSB Speed to RAM Clock (4:3 in this case)]

If the DDR Clock is too high, meaning, if I forgot to change the RAM clock to 166, and left it at 200, the DDR clock would have clocked to 250MHz, and since my RAM can only do 200MHz (actually, a little over 200, since I have it at 208)… it will make the system VERY UNSTABLE at 250

Bus Speed: 1000MHz [FSB Speed x HT Multiplier] = [250 x 4]

As with the DDR clock, since my mobo can only work with an FSB of 1000MHz, if I do 250 x 5 (1250MHz) the system will be VERY UNSTABLE